Ments



March 13, 1928. Re. 16,901

N. H. HOLLAND ELECTRIC SYSTEM Original Filed July 13. 1920 2 Sheets-Sheet 1 ATTORNEY March 13, 1928. Re. 16,901

N. H. HOLLAND ELECTRIC SYSTEM inal Filed July 13. 1920' 2 Sheets-Sheet 2 q A,

! I I I I I I I w I I INVENTOR BY gzaflkm ATTORNEY Reissue cl Mar. 13, 1928.

Remain PATENT OFFICE.

NEWMAN n. HOLLAND, OE MONTCLAIR, EW JERS 'ASSIGNOR, Y MEsNE AssIGN- MENTS, T0 THOMAS A. EDISON, INCORPORATED, OE WEsT ORANGE, NEW JERSEY,

A CORPORATION OE NEW JERSEY.

ELECTRIC SYSTEM.

Original No. 1,49s,2ss, datedlune 17, 1924, Serial No. 395,897, filed July, 13, 1920. i reissue filed June 11, 1926. Serial No. 115,353.

My invention relates to electric systems and more particularly to signaling systems such as automatic railway block or other railway signaling systems and control systems whereintrack circuits or othercircuits containing or associated withrelays or other control devices are employed to control signal circuits or signal-control circuits or other circuits; the present invention in some aspects being an improvement on the invention disclosed in Patent No. 1,405,005,,en-

titled Signaling systems and granted Jannary 31, 1922, on an-application of Isaac P. Rodman.

In practically all signaling on control systems of this character now in use, the track or other control circuits are supplied either with direct current from primary. or storage batteries, or with alternating current of given frequencies fed thereto from high voltage transmission lines by, transformers.

Vhere in a railway signaling system, directcurrent track control circuits are used, there is more or less danger of failure of operation of the signal for a given block or track section, by reason of the entrance of stray currents into the corresponding track circuit from outside sources, such, for example, as an adjacent track circuit. Where alternating-current track or control circuits. are employed, the same are, of course, lmmune to stray direct currents, but are likely to be seriously affected by stray alternating currents coming from sources wholly-outside the system. This is due to the fact that the great majority of alternating-current circuits now usedare supplied with commercial alternating currents at certain frequencies and alternating currents of the same frequencies are often used in alternating-current signaling or control systems. .Moreover,

the prcsent-day types of alternating-current Application for tion is to provide an improved, and an extremely simple and eflicient signaling or control system which has all the advantages of present-day alternating current railway signaling or control systems as regards interference by stray or foreign direct currents, which Will be unaffected b 1 stray currents from alternatingcurrent circuits supplied with commercial alternating currents, and wherein its unnecessary to employ polarized circuits, or line-control circuits, or a transmission line for supplying current to the different track or other control circuits.-

Another and also one of the principal objects of my invention is to provide a signaling or control system of this character wherein current variations such as directcurrent pulsations or alternating currents are produced in the track circuits or the circuits containing or associated with the relays or other devices for "controlling the signal circuits-or signal-control or'o'ther circui'ts by means comprising a novel type of pulsating-current generator and suitable.

sources of direct current such as primary or 712,180, filed May 10, 1924, entitled Signa-ling systems or the like,, and a division-of the application for the said Patent No.

1,4.98 238, sought 'to be reissued bythe pres entiapplicati'on,.Ihave described and-claimed the. novel forms of pulsating current generator and relay referred to above.

More specifically described, myinvention as applied to a railway signaling system, consists in producing in each track circuit of such aisystem, by the use of sources of direct current such as primary or storage batteries, current variations such as directcurrent pulsations Or' alternating current, of a givenfrequency and preferably, dlfierent from the frequency of the current variations produced in any adjacent track circuit, and

associating with each t-rack c-ircuit a relay or other control device for controlling the corresponding signal or signal-control circuit andwhich is tuned to thefrequency of thecurrent yariations produced such track circuit. I preferably employ as the means for producing current variations in each 7 track circuit, a direct-current circuit suption whereby direct-current pulsations of a' plied with current from a primary battery or other suitable source and containing a resistance means such as aniicrophone, the resistance of which is variable by vibration, and a. vibratory means such as a reed and preferably a tuning fork positioned so as to affect such resistance means by its'vibradefinite period or frequency corresponding to the natural period of vibration of said reed will be produced in such direct-current circuit. The relayor other controldevice for controlling the corresponding signal circuit is tuned either mechanically or electricallyor both mechanically and electrically, preferably the latter, to the frequency of the current-variations thus produced in the track circuit, and the arrangement is preferably such that the frequency of the directcurrent pulsations or the alternating current .5 thus applied to each track circuit is different from that supplied to any adjacent track circuit and preferably also different from the frequencies of any stray currents such as the commercial alternating currents usually employed for the propulsion of trains on railroads or other purposes. V Other features and objects of my invention will be hereinafter more fully described and claimed.

In order that. my invention may be more clearly understood, attention is directed'to the drawings accompanying and forming'a part of this specification, and in which:

Figure 1 is a diagrammatic viewillustrating a portion of one form of an automatic railway block signaling system in accordance with my invention, in which the current variations'p roduced in the track circuits associated with the relays for control ling the'signal or signal-control circuits are direct-current pulsations,,and'in which the circuits containing or associated with the re-, lays have'produced therein alternating currents of frequencies respectively correspond-j ingto the frequencies of the direct-current pulsations in the track circuits, the relays in this case being'both mechanically and electrically tuned; I

Fig. 2 is a diagrammatic view illustrating a modification of the system shown in Fig. 1, in which the relays for controlling the signal or signal-control circuits are only mechanically tuned and are includedin the track circuits, and in which the current variation's produced in the latter circuits are direct-current pulsations;

Fig. 3 is a viewsimilar I another form of signaling system in accordance with my invention, in which the track circuits are supplied with alternating cur-,

rents and in which the relays for controlling contact'2l. to Fig. 1, showing the signal or signal-control circuits are electrically tuned to the frequencies of the said alternating currents in the track circuits; and I Fig. 4 is a. view illustrating a slight modification of the system shown in Fig. 3.

Referring to the drawings and especially to Fig. 1, reference characters A, B andC represent three track sections or blocks of a railway signaling system in accordance with my invention, and S the signal asso- 'ciated with and disposed at the entrance of the section or block B for governing the same; it being understood that similar signals are disposed at the entrance of all other blocksof the'system. Reference character M represents a primary battery one side of which is connected to one rail 1 of the section 13' at the exit end thereof by means of conductor 2, and the other side of which is connected to the rail 3 of section B at the exit end thereof through conductor 4, con ductor 5, microphone 6 and conductor 7. The microphone 6 is mounted on a suitable support E on which is also mounted a vibratory reed such as a tuning fork 8. An electro-magnet 9 is disposed adjacent one leg of the tuning fork 8, and one end of the coil "of this electro-magnet is connected to one side of the battery M through conductors 10 and 2, while the'other end of said coil is connected to the other side of the battery M through conductor 11, microphone 12 and conductors 13 and 4. The microphone 12 is also mounted onthe support E and it will accordingly be apparent that both of the microphones 6 and 12 will be affected by At the envibrations of the tuning fork. trance end of the section or block B, the rails 1 and 3 are respectively connected by 'means of conductors 14 and lf) to the primary 16 ofa transformer, the secondary 17 of the transformer being connected in circuit with the electro-magnet 18 of a relay.

The armature of the relay consists of a vi-.

bratory reed, preferably a tuning fork 19, mounted on a suitable support F and having the'same natural period of'vibration as the tuning fork 8. This'tuning fork 19 controlsxa switch K which is located in a circuit to be controlled such as the signal or signal-control circuit for signal S and which comprises two spring contacts 20 and. 21 fixed at one end. The spring contact 20 comprises two arms 22 and 23, and normally assumes aposition with its arm engaging one leg of the tuning fork 19*and with its arm 23' in opposed spaced relation at its upper end to 'the upper end of the spring Suitable means is provided for effecting a relative adjustment of the contacts 20 and 21, this means as shown consisting of a screw 24 threaded through a suitable support and coacting with the conof the" latter tOWfiI-dS and away from the upper end ofthe arm 23 of the "contact "20. Reference character N represents a suitable source o'f-current such as a primary or storage battery for supplying current to the circuit to be controlled, suchas the signal or signal-control circuit for signal S, one side of the battery being connected to themo'tor, (not shown) disposed in the casing Gyfor actuating the signal S, by means of conductor 25, and the other side thereof beingconnected to contact20 of switch K by conductor26. The signalactuating motor in casing G- is also connected to switch contact 21 by means ofconductor 27. When the signal or signal-control circuit is opened, the signal actuating motor in casing G will, of course, cease to operate and the signal S will thereupon, under the action of gravity, drop to danger position as shown; but when this circuit is closed, the motor will move the signal S to andhold the same in clear position as indicated in dotted line.

The operation of that form of my invention shown in Fig. 1'is as follows: Direct current is, continuously supplied to the track circuit section B over the following path: From battery through conductor 2, rail 1, and conductor '14 to the primary -16 of the transformer, then through conductor 15,

rail 3, conductor 7 microphone 6, conductor .5 and conductor A back to the battery. Direct-current will also be continuously supplied to a second circuit over the following path: From the battery M through conductor 2, conductor 10, the coil of electro-m-ag net 9, conductor 11, microphone =12, conductor 13 and conductor 4 back tothe battery. This second circuit together with the tuning for-k 8 disposed in operative relation to the electro-magnet 9 comprise a pulsating current generator, for when this circuit is made, the electro-magnet '9 attracts the tuning fork 8 and starts the same vibrating in its natural period, the tuning fork Sin Vibrating, Vlbrates the support E and microphone '12,

thereby producing changes or variations in the resistance of the microphone 12 corresponding in frequency to the vibrations of the tuning fork which turn effects current variations or pulsations in the circuit including the coil of electro-magnet 9. It is therefore apparent that the tuning fork will be continuously vibrated in its natural period as long as said circuit is closed and supplied with current. The vibrations of the tuning fork 8 alsoefi'ect variations of i the. same frequency in the resistance of the microphone 6, and accordingly direct-current pulsations ofa frequencycorresponding to the frequency of the natural period of vibration of the tuning fork 8 are produced in the trackcircuit including the primary 16 of the transformer. Of course, it is not necessary to connect the electro-magnetytl and microphone 12 in :shunt with the track circuit as 'sh'own,for the same results may be obtained by using a single microphone and connecting the same and theelectro-magnet in series with the tr'ack circuit. Obviously alternating current of a frequency corresponding to the'frequency of the direct-current pulsations in the track circuit, will be produced in the circuit of the secondary 17 of'the transformer and the electro-magn et 1-8 of the relay controlling the signalor signalcontrol circuit. The relayis suitably electrically tuned to the frcquency-ofthe alter nating current thus produced in the circuit of the secondary 17 of the transformer. and the electro-magnet 18, and, therefore, to the frequency of the direct-current pulsations in Cally tuned to the frequencyof-the alternating current in the circuit of the electro-Inagnet 18 and secondary 17 of the transformer and, therefore, to the frequency of the directcurrent pulsations produced in the track circuit by thepulsating-current generator. The

tuning fork 19 will, therefore, assuming the section or "block B to be uno'ccupied, be vibrated' in its natural period and, by reason of the engagement of one leg thereof with the armQQ of, the spring contact 20, will normally maintain the 'lattervin circuit clos-' ing position with the arm 23thereof in engagement-with the spring contact 21. In this connection it is to be noted that the spring contact '20 should have a natural period of vibration different from and preferably 'much'less than the natural period of vibration of the tuning fork 19. Switch K thus being maintained closed, current will be supplied to the signal actuating motor and the signal S will be normally held in clear position-as explained above. Vhen a train T moves into the section or -block B, as shown, the primary 16 of the transformer will be short -circuited and accordingly the electro-magnet .18 of the relay will be deenergized. The tuning fork 19 will'thereupon .cease to vibrate, the spring contact of switch will move to and remain in open position, the motor in casing G will cease to operate and the signal vS will, under the action of gravity, drop to danger position,

as shown. When the train T- moves out of 1 the sect-ion or block B, the relay controlling I the signal "or signal-control circuit will again be :operated as above described, said circuit will be closed and the signal returned 'to clear position.

v In the modified system shown in Fig. 2," the rails 1 and 30f section orblock Byare directly connected at the entrance end of the sectionby means of conductors 14 and 15, respectively corresponding to the con-.-

ductors 14 and 15. shown in Fig.1, to the coil of the electro-magnet 18 of the relay for controlling the signal or signal-control,

circuit instead of to the primary of a trans former. Accordingly, direct-current pulsations of a frequency corresponding to the frequency of the tuning fork of the pulsating-current generator are produced in the circuit of the coil of the electro-magnet 18. Therefore,'in this form of my invention, the

relay of which'the electro-magnet 18' is a part, is tuned tothe direct-current pulsations produced by the pulsating-current generator only by reason of the fact that the tuning fork 19 comprising the armature of the relayhas the same natural period of vibration as'the tuningfork of such generator. It will be apparent that when the section B is unoccupied, the electro-magnet 18 will be supplied With direct-current pulsations and effect the vibration of the tuning fork 19 in its natural period. Except as just described, the construction, arrangement and operation of this form of my invention and that shown in Fig.4 are the same.

In the modification shown 'in Fig. 3, the conductors 2 and 7 respectively corre sponding to the conductors 2 and ,7 of the 7 system shown in Fig. 1,.instead of being respectivelfi connected to the rails l and 3 of section are connected to the primary 29 of a transformer. The secondary 30 of this transformer is connected by conductors 31 and 32 across-the rails land 3 of the section B at .the exit end thereof, and said rails are respectively connected at the entrance end of the section B by means of conductors 14 and 15 to the terminals of the coil of the electro-ma-gnet 18 comprising a part of the relay for controlling-the signal or signal-control circuit for signal S. The armature of therelay consists of a pivoted arm 33 constituting a part ofa switch K in the signal or signal-control circuit. In this form of my invention the track circuit is as follows: From one terminal ofv the secondary 30 through conductor 31, rail 1, conductor 14 the coil of electro-lnagnet 18 conductor 15 rail 3 and conductor 32-, to the other terminal of the secondary 30. It will be apparent that directc'urrent pulsations of a frequency corresponding to the frequency of the vibrations of the tuning fork 8 will be produced in the circuit of the primary 29' of the transformer, such circuit being as follows: From the battery M through conductor 2, primary 29, conductor 7,'microphone 6, conductor 5 and conductor 4 back to the battery. Alternating current of a frequency corresponding to the frequency of the direct-current pulsations in the circuit of the primary'29 will therefore be produced in the track circuit including the secondary 30 of the transformer, and

when the. section or block B is unoccupied, the electro-magnet 18 will be energized, for the latter is suitably electrically tuned, as by means of the adjustable condenser D to alternating current of such frequency. The armature 33 will thereupon be moved to a position closing the signal or signal-control circuit for signal S" and the latter will accordingly be moved to clear position. Whena train T enters the section or block B, the electro-magnet 18 will be short-circuited, whereupon the armature 33 will antomatically move to a position opening the signal or signal-control circuit, and the signal will move to danger shown.

In that form of my invention illustrated in Fig. 4, the conductors 14 and 15 respectively corresponding to the conductors 14 and 15 of the system shown in Fig. 3, instead of being directly connected to the coil of the position, as

elect-ro-magnet 18 of the relay controlling the signal or signal-control circuit, are connected to the primary 34 of a transformer.

I The secondary 35 of this transformer is connected by conductors 36 and 37 to the terminals of the coil of'the electro-magnet18 of the relay. Suitable means, such as an adustable condenser D is connected in circuit with the coil of the electro-magnet for the.

purpose of electrically tuning the relay to the frequency of the alternating currents produced in the circuit of said coil and in the track circuit, and therefore to the frequency of the direct-current pulsations produced in the circuit of the primary 29 as well as to the-frequency of the vibrations of the tuning fork 8 of the pulsating-current generator. The purpose of the trans- ,formercomprising the primary 34 and secondary 35 is merely-t0 enable the voltage of the alternating current produced inthe circuit of the electro-magnet 18 to be stepped up or down as desired with respect to the voltage of the alternating current produced in the" track circuit. 'Except as just described, the construction, arrangement and 'operationof this form of my invention and that shown in Fig. 3 are the same.

' While with respect to'each form of the invention disclosed herein, I have shown and described the circuit connections for only one track section or block, it is to be understood that similar circuitconnections operating in a. similar manner, are'p rovidedfor all other sections or blocks. The arrange- Lil be no danger of'the relay'for any section being affected by stray currents from the circuit connections; of any adjacent section.

\Vhile I have shown several embodiments of my. invention, it is to be understood that these are for the purposes of illustration only and that such embodiments are subject to numerous changes and modifications without departure from the spirit of, the invention and the scope of the appended claims. It is also to. be understood that while I have shown and specifically described my invention as applied to railway signaling s stems, it is equally well adapted, as to its principal features at least, for

application to various other electric sys-. terms including automatic train-control systems.

Having now described my invention, what I claim as new and desire to protect by Letters Patent of the United States, is as follows:

1. In an automatic railway block signal ing system, a direct-current circuit which is constantly. closed during operation oft-he system, means comprising a vibratory reed which. is extraneousto all circuits of the system for producing current pulsations of a given frequency in the directcurrent 01rcuit, a signal circuit,'and means for controlling said signal circuit comprising a device normally in operative relation to said directcurrent circuit and tuncdtothe frequency of the current pulsations in the latter, the presence of a. train in a block with which said signal circuit is associated, placing said device in inoperative relation to saith directcur-rent circuit, substantially as described.

2. In an: automatic railway block signal.- ing system, a signal circuit, and meansfor controlling said signal circuit, comprising a direct-current circuit which is constantly closed during'operation of the system, means comprising a vibratory reed which is ex: traneous to all-circuits of thesystemfor; producingv current pulsations ofa'given frequency in said direct-current circuit, and a relay normally in operative relation to said direct-current. circuit and tuned to thefrequency of the current pulsations inthe latter for controlling the signal circuit, the pres:

ence of a train in a block with which the signal circuit is associated, placing said relay in inoperative relation to said direct-current circuit, substantially as described.

3. In an automatic railway block signaling system, a signal circuit, a direct-current circuit which is constantly closed during operation of the system, means'comprising a vibratory reedjwhich is extraneous to all circuits of the system for producing current pulsations of a given frequency insaid direct-current circuit, the tracksection of; the block with which said signal circuitisa'ssd ciated being electrically associated withsaid direct-current circuit whereby current variations of a frequency corresponding to the frequency of the pulsations in the directcurrentcircuit are produced in said track section, "and a relay tuned to thei'requency of the current variations produced in the track section for controlling'the signal circuit, said relay being electrically associated with said track section so as to be normally responsive to the current variations produced in. the latter, the presence of a train in said track, section rendering said relay unresponsive to the said, current variations, substantially as described.

4:. In an automatic raliway block signal ing system, a signal circuit, for eachof a plurallty of blocks,- and means for controll ng each signal circu t comprismg a directcurrent circuit which is constantly closed during operation of the system,.means com,- prising a vibratory reed whichis extraneous to all circuits ofithe, systemfor producing current pulsations, of a given frequency 1 in said direct-current circuit, and a: relay nor.- mally in operative relationwtosaid direct: current circuit and t uned to the frequency of the current pulsations-in the latter, the presence of atrain in a, corresponding block placing said, relay in inoperative relation to said direct-current circuit, the frequency of the current pulsations produced in' the said direct-current circuit for any given block the frequency of the current pulsations in the latter, the presence of a train in a block with, which said. slgnallcircuit is associated", placing sald device in inoperative relation to said direct-current circuit, substantiallyas described, t t v 6. In an automatic railway block signaling system, a direct-current circuit which is constantly closed during operation of the system, means comprising a. vibratory reed which is extraneous to all circuitsof the system for producing current pulsations of agiven frequency in the directrcurrent circuit, a signal circuit, andineansfor, controlling said signal. circuit comprising a device normally in operative relation tosaid direct: current, circuit and mechanically and electri callytuned to the frequency of the current i no pulsations in the latter, the presence of a train in a block with which said signal circuit is associated, placing said device'in inoperative relation to said direct-current circuit,substantially as described.

,7. In an automatic railway block signaling system, a signal circuit for each of a plurality of blocks, and means for controlling each signal circuit comprising a directcurrent circuit which is constantly closed during operation of the system, means comprising a vibratory reed which is extraneous to all circuits of the system for producing current pulsations of a given frequency in said direct-current circuit, and a relay which is normally in operative relation to said direct current circuit and which comprises a reed tuned to the frequency of said current pulsations, the presence of a trainin the corresponding block placing said relay in inoperative relation to said direct-current circuit, substantially as described.

8. In an automatic railway block signaling system, a direct-current circuit which is constantly closed-during operation of the sys-' tem, means comprising a vibratory reed which is extraneous to all circuits of the syshim for producing current pulsations of a given frequency in the direct-current cir cuit, a signal circuit, and means normally in operative relation to said direct current circuit for, controlling said signal circuit and comprising a reed tuned to the frequency of said current pulsations, the presence of a train in a block with which said signal circuit'is associated, placing said controlling means in inoperative relation to said directcurrent circuit, substantially as described.

'9. In an automatic railway block signaling system, a direct-current circuit which is constantly closed during operation of 'the system and which includes the primary ofa transformer, a circuit including the secondary of the transformer, the rails of-a block or tracksection.beinglinclude'd in one of said r circuits, means comprising a vibratory'reed which is extraneous to all circuits of the sys-- tem for producing direct-current pulsations of agiven frequency in'the said primary included in the direct-current circuit wherebyan alternating current of the same frequency is produced in the other of said circuits, a signal circuit, andarelay'for con trolling said signal circuit associated with the circuit in which the alternating current is produced, said 'relay being tuned to the frequency of said alternating current, substantially as described. 1 A,

10. In an automatic railway block.signaling system, a. direct-current circuit which is. constantly closed during operation of the system and which includes the primary of a transformer, a circuit including the secondary of the transformer, the rails of a block or track section being included in one of sa d circuits, means comprising a vibratory reed which is extraneous to all circuits of the system for producing current pulsations of a given frequency in the direct-current'circuit whereby an alternating current of the same frequency is produced in the other of said circuits, a signal circuit, and a relay for controlling said signal circuit associated with the circuit in which the alternating current is produced and mechanicallytuned tofthe frequency of said alternating current, substantially as described. i

11. In anautomatic railway block signaling system, a direct-currentcircuit which is constantly closed during operation of the system and which includes the primary of a transformer, a circuitincluding the secondary of the transformer, the rails of a block or track section being included in one of said circuits, means'comprising a vibratory reed which is extraneous to all circuits of the system for producing current pulsations of a given frequency in the direct-current.

circuit whereby an alternating current of the same frequency is produced in the other of said circuits, a signal circuit, and a relay for controlling said signal circuit associated with the circuit in which the alternating currentis produced and mechanically and electrically tuned to the frequency of said alternating current, substantially as describeth l 12. In an automatic railway block signaling system, a direct-current circuit which iscOnstantlycIOsed during operation of the system and which includes the primary of a transformer, a circuit including the secondary of the transformer, the rails of a block or track section being included in one of said circuits, means comprising a vibratory.

reedwhich is extraneous to all circuits. of the system for producing current pulsations of'a given frequency in the direct-curernt circuit whereby an alternating current of the same frequency is produced in the other of said circuits, a signal circuit, and a relay the frequencyof said alternating current,

is constantly closed during operation of the iiU system and which includes the primary of a transformer, a circuit including the secondary of the transformer, the rails of a block or tracksection being included'in one of said circuits, means comprising avibratory reed which is extraneous to all circuits of the, system and which is vibrated-at its natural I period for producing currentpulsa'tions of a given frequency "in the directcurrentcir-- cuit whereby an alternating current of the same frequency is produced in the other of said circuits, a signal circuit, and a relay for controlling said signal circuit associated with the circuit in which the'alternating current is produced and tuned to the frequency of said alternating current, substantially as described.

14. In an automatic railway block signaling system, a direct-current circuit including the primary of a transformer, and a circuit including the secondary of the transformer, the rails of a block or track section being includedin one of said circuits, means comprising a vibratory-reed independent of said direct-current circuit and vibrated at its natural period and amicrophone in said direct-current circuit, said microphone being inspaced relation to said reed so as not to be engaged by the latter in the vibration thereof, but being positioned so asto be afiected by the vibrations of the reed, for producing current pulsations of a given frequency in the direct-current circuit whereby an alternating" current of the same frequency is produced inthe other of said circuits, a signal circuit, and: arelay for controlling said signal: circuit associated withthe circuit in which thealternating current isproduced and tuned to the frequency ofsaid alternating current, substantially as described. i

15. In an automatic railway block signaling system, a direct-current circuit, resistance means included. in". said, circuit, the resistance of which is affected by vibration thereof, means comprising a vlbratory member which is extraneous to all circuits of the system for vibrating said resistance means to thereby produce current pulsations of a given frequency in said direct-current circuit, a signal circuit, and means for controlling said signal circuit comprising a decurrent pulsations of a given frequency in such circuit, a second circuit, and means for controlling said second circuit comprising a device 0 eratively associated with and tuned to the requency of the current pulsations produced in said direct-current circuit, sub stantially as described.

17. In an electrical system, a direct-current circuit, means including vibratory [means which is extraneous to all circuits of the system for producing current pulsations of a given frequency in. the latter, a. second j scribed. a

18. Inan electrical system, a direct-cur.- rent circuit which is constantly closed during operation of thesystem, means including vibratory means which. is extraneous. to. all circuits of the system for. producing current pulsations of a. given frequency in said: circuit, asecond circuit, and means. 'operatively associated with said direct-current circuit and adapted to control said second circuit, substantially as described.

19. In an electrical system, a: direct-current'circuit which. is constantly closedduring operation Off the system, means including vibratory means which is extraneous to all circuitsof the systemfon producing current pulsations of a given frequency in said circuit, a second, circuit, and means forc'ontrolling said second circuit comprising a. device operatively associated with and tuned to the frequency of the current pulsations produced in said. direct-current' circuit, substantially as described.

20. In an electrical system, a direct-current circuit which is constantly closed, during operation of the system, meansincluding vibratory means whichv is extraneousto; all circuits of the system for producing current pulsations of; a: given; frequency iathe; directcurrent circuit, a second circuit, and means for controlling said second circuit comprising a device operatively associated with and tuned to the frequency of the current pulsations produced in said direct-current circuit, substantially as described.

21. In an electrical system, a direct-cur rent circuit which is constantly closed dur-.

so V

lit)

ing operation of the system and which includes the primary of a transformer, a

'secondcircuit including the secondary of the transformer, means including vibratory means which is extraneous to all circuits of the system for producing direct-current pulsations of a given frequency in said directcurrent circuit whereby an alternating current of the same frequency is produced in the said second circuit, a third circuit, and means operatively associated with said sec ond circuit and adapted to control said third circuit, substantially as described.

22. In an electrical system, a direct-current circuit which is constantly closed during operation of the system and which includes the primary of atransformer, asco- 0nd circuit including the secondary of the transformer, means including a vibratory sations of a given frequency in said directcurrent pulsations of a given frequency in.

said direct-current circuit whereby an alternating current of the same frequency is produced in the said second circuit, a third circuit, and means forcontrolling said third circuit comprising a device operatively associated with and tuned to the frequency of the alternating current produced'in said sec, ond circuit, substantially as described.

24. In an electrical system, a direct-current circuit including the primaryofatransformer, a second circuit including the secondary of the transformer, means comprising a vibratory reed which is extraneous to allcircuits of the system vibrated at its natural period for producing current pulsations of a given frequency in the direct-current circuit whereby an alternating current of the same frequency is produced in said second circuit,-a

third circuit and a relay for controlling said third circuit, said relay being operatively associated with said second circuit and tuned to the frequency'of the alternating current produced therein, substantially as described.

25; In an electrical system, a direct-current circuit. including the primary of .a transformer, a second circuit including the secondary of the transformer, means comprising a tuning fork vibrated at its natural period and a microphone in said direct-current circuit, said microphone being in spaced relation to said tuning fork so as not to be engaged by the latter in the vibration thereof, but being positioned so as to be affected by the vibrations of the tuning fork for producing current pulsations of a given fre- 26. In an electrical system, a directcur rent circuit, means including Vibratory means which is extraneous to all circuits of the-system for producing current pulsations of a given frequency in the direct-current circuit, a second circuit, and means operativelyassociated with said direct-current cirs cuit and adapted to control said second circuit, substantially as described.

This specification signed this 9th June, 1926. 5 NEWMAN H. l HOLLAND.

day of 50 quency in the direct-current circuit whereby Y 

